RESUMEN
Previous study of transgenic mice with long-term expression of pleiomorphic adenoma gene-like 2 (PLAGL2), a surfactant protein C (SP-C) transactivator, in type II cells showed the manifestation of centrilobular emphysema in vivo. Since emphysema is an independent risk factor for bronchogenic carcinoma, we hypothesized that the mouse lungs with induced PLAGL2-expression had increased incidences in developing lung adenocarcinoma. To test the hypothesis, mouse lungs were examined for the presence of tumors. Male mice with induced PLAGL2-expression in the lungs were more vulnerable to tumorigenesis than female mice (p<0.05). Epithelial cells expressing pro-SP-C and Clara cell secretory protein (CCSP) at the terminal bronchioles and the bronchoalveolar duct junction (BADJ) were increased in the induced transgenic mice, suggesting a role of PLAGL2 in expanding SP-C expression cells. Co-expression of TTF-1, pro-SP-C and CD133 (a stem-cell marker) in cancer and distal airway epithelial cells indicated that both cells were derived from common progenitors. This result supported a common-cell-origin mechanism for the comorbid diseases - emphysema and lung cancer. Furthermore, a public lung cancer gene expression profiling database was examined to determine the relevance of PLAGL2 expression and lung adenocarcinoma in humans. Patients with high PLAGL2 expression in lung tumors were readily found. Female patients (N=218) with low PLAGL2 expression (the lowest quartile of total patients) at the early-stage of disease had better prognosis in survival. Male patients, on the other hand, had no such correlation. Generally, their survival rate was significantly poorer than of female patients. Taken together, our data suggested a pathological role of PLAGL2 in lung adenocarcinoma development and a preferable prognosis of low PLAGL2 expression in female patients.
Asunto(s)
Adenocarcinoma/diagnóstico , Adenocarcinoma/epidemiología , Proteínas de Unión al ADN/metabolismo , Neoplasias Pulmonares/diagnóstico , Neoplasias Pulmonares/epidemiología , Enfisema Pulmonar/diagnóstico , Enfisema Pulmonar/epidemiología , Proteínas de Unión al ARN/metabolismo , Factores de Transcripción/metabolismo , Antígeno AC133 , Adenocarcinoma/mortalidad , Adenocarcinoma/patología , Animales , Antígenos CD/genética , Antígenos CD/metabolismo , Comorbilidad , Proteínas de Unión al ADN/genética , Femenino , Glicoproteínas/genética , Glicoproteínas/metabolismo , Células Madre Hematopoyéticas/metabolismo , Células Madre Hematopoyéticas/patología , Humanos , Neoplasias Pulmonares/mortalidad , Neoplasias Pulmonares/patología , Masculino , Ratones , Ratones Transgénicos , Células Madre Neoplásicas/metabolismo , Células Madre Neoplásicas/patología , Péptidos/genética , Péptidos/metabolismo , Pronóstico , Enfisema Pulmonar/mortalidad , Enfisema Pulmonar/patología , Proteína C Asociada a Surfactante Pulmonar/genética , Proteína C Asociada a Surfactante Pulmonar/metabolismo , Proteínas de Unión al ARN/genética , Mucosa Respiratoria , Riesgo , Factores Sexuales , Análisis de Supervivencia , Factores de Transcripción/genética , Carga TumoralRESUMEN
Emphysema and bronchitis are major components of chronic obstructive pulmonary disease (COPD). Pleomorphic adenoma gene like-2 (PLAGL2), a zinc finger DNA-binding protein, is a transcription factor of the surfactant protein C (SP-C) promoter. Using an inducible transgenic mouse model, PLAGL2 and SP-C were ectopically expressed in lung epithelial cells of terminal bronchiole including the bronchoalveolar duct junction (BADJ), where only few cells express both genes under normal conditions. Ectopic PLAGL2 was also expressed in alveolar type II cells of induced mice. The overexpression of PLAGL2 was associated with the development of air space enlargement in the distal airways of adult mice. Defective alveolar septa and degraded airway fragments were found in the lesions of emphysematous lungs, indicating chronic airway destruction. Female mice were particularly sensitive to the effects of PLAGL2 overexpression with more dramatic emphysematous changes compared with male mice. In addition, analysis of the respiratory system mechanics in the mice indicated that the induction of PLAGL2 resulted in a significant increase in respiratory system compliance. Both TdT-mediated dUTP nick end labeling (TUNEL) and caspase-3 analyses showed that apoptotic activity was increased in epithelial cells within the emphysematous lesions as well as at the BADJ. Our results indicate that increased cell injury and/or death could be caused directly by the upregulation of PLAGL2 downstream gene, bNip3, a preapoptotic molecule that dimerizes with Bcl-2, or indirectly by the aberrant expression of SP-C-induced endoplasmic reticulum stress in epithelial cells. Finally, increased expression of PLAGL2 in alveolar epithelial cells correlated with the development of emphysema in the lung of COPD patients. In summary, our data from both animal and human studies support a novel pathogenic role of PLAGL2 in pulmonary emphysema, a critical aspect of severe COPD.
Asunto(s)
Bronquiolos/patología , Proteínas de Unión al ADN/metabolismo , Epitelio/patología , Proteínas de la Membrana/metabolismo , Proteínas Mitocondriales/metabolismo , Alveolos Pulmonares/patología , Enfisema Pulmonar/metabolismo , Proteína C Asociada a Surfactante Pulmonar/metabolismo , Proteínas de Unión al ARN/metabolismo , Factores de Transcripción/metabolismo , Anciano , Animales , Bronquiolos/metabolismo , Bronquiolos/fisiopatología , Muerte Celular , Células Epiteliales/metabolismo , Células Epiteliales/patología , Epitelio/metabolismo , Femenino , Humanos , Rendimiento Pulmonar/fisiología , Masculino , Ratones , Ratones Transgénicos , Persona de Mediana Edad , Alveolos Pulmonares/metabolismo , Alveolos Pulmonares/fisiopatología , Enfermedad Pulmonar Obstructiva Crónica/metabolismo , Enfermedad Pulmonar Obstructiva Crónica/patología , Enfermedad Pulmonar Obstructiva Crónica/fisiopatología , Enfisema Pulmonar/patología , Enfisema Pulmonar/fisiopatología , TransgenesRESUMEN
Pleomorphic adenoma gene like-2 (PLAGL2), a developmentally regulated and stress inducible zinc finger protein can be post-translationally modified by small ubiquitin-like modifier peptide (SUMO-1); and SUMOylation attenuates PLAGL2 activity on the interactive promoter. Since PLAGL2 was a transactivator of the surfactant protein-C (SP-C) promoter, we hypothesized that SUMOylation down-regulated PLAGL2-activated SP-C promoter activity. Unexpectedly, the SUMO-conjugating enzyme Ubc9 enhanced, rather than reduced, PLAGL2 activated promoter activity but did not affect TTF-1 activation of the promoter. Ubc9 mutant (Ubc9-C93S) defective in SUMO-conjugating activity also enhanced PLAGL2-driven promoter activity suggesting that the stimulatory effect of Ubc9 on SP-C promoter activation was independent of its enzymatic function. PLAGL2 mutants without the K250 and/or K269 SUMOylation sites did not further improve PLAGL2 programmed transcription nor did they abolish Ubc9 enhanced promoter activity supporting the SUMOylation-independent mechanism. Chromatin immunoprecipitation (ChIP) assay demonstrated the association of PLAGL2 and Ubc9 with the SP-C promoter in vivo. Taken together, our data suggests that Ubc9 can function as a co-factor of PLAGL2, uncoupling from its enzymatic activity, to mediate PLAGL2 interactive SP-C promoter activity.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Proteína C Asociada a Surfactante Pulmonar/genética , Proteínas de Unión al ARN/metabolismo , Factores de Transcripción/metabolismo , Activación Transcripcional , Enzimas Ubiquitina-Conjugadoras/metabolismo , Línea Celular Tumoral , Inmunoprecipitación de Cromatina , Humanos , Pulmón/metabolismo , Regiones Promotoras Genéticas , Proteína SUMO-1/metabolismoRESUMEN
Expression of surfactant protein (SP)-C occurs principally in type II pneumocytes located in the distal lung alveolae. SP-C expression is thought to be primarily regulated by thyroid transcription factor (TTF)-1 and its associated proteins interacting with a previously defined promoter region between -197 and -158 in mice. We screened a human lung cDNA library using a modified yeast one-hybrid system and identified pleiomorphic adenoma gene-like (PLAGL)-2, a ubiquitously expressed zinc finger protein, as a transfactor of the SP-C promoter. The PLAGL2 DNA-binding site was located in the SP-C promoter proximal region close to the TTF-1 sites. This site was demonstrated to be functional by use of electrophoresis mobility shift assay, mutagenesis analysis, and transfection studies. PLAGL2 bound to DNA via its N-terminus zinc fingers and activated the SP-C promoter in a TTF-1-independent manner. Both human and mouse SP-C promoters, but not the SP-B promoter, could be activated by PLAGL2 in transfected human embryonic kidney-293 (HEK293) cells as well as in murine type II (MLE12) cells. The expression of PLAGL2 in isolated human embryonic lung type II cells and its transactivation activity on the SP-C promoter suggest that PLAGL2 may modulate SP-C expression during lung development.